Pressure-balanced stab connection

Abstract

Apparatus for connecting portions of subsea flow conduits includes a stab member with a body and having a bore therethrough, one end of which exits from the stab body through a side port. A stab receptacle includes a bore for receiving the stab body, and a flow bore intersecting the receiving bore and leading to the exterior of the receptacle. The side port communciates with the receptacle flow bore when the stab member is landed in the receiving bore. Seals above and below the side port seal the receiving bore above and below the intersection of the receptacle flow bore and receiving bore. The cross-sectional areas of the seals exposed to internal fluid pressure are substantially equal, resulting in zero blow-apart force on the stab connection. Alternatively, the lower seal can have a larger exposed cross-sectional area than the upper seal, resulting in a net force tending to hold the connection teogether. Split retainer rings having external chamfer surfaces are mounted on the stab body above and below the lower seals. The retainer rings are disposed in grooves allowing the rings limited sliding radial movement with respect to the stab body. The stab receptacle is mounted to a support frame with relatively long, thin, vertically disposed studs which resist vertically directed forces but permit lateral and rotational deflection of the stab receptacle when acted upon by non-vertical forces. The stab body bore and receptacle flow bore include shaped portions to reduce turbulence of fluids flowing therethrough.

We claim: 
     
       1. Apparatus for sealingly connecting a flow bore of a wellhead to a flowline, comprising: a stab member including a stab body, said stab body having a stab body bore therethrough, one end of said stab body bore exiting from said stab body and being in fluid communication with the flow bore and the other end of said stab body bore exiting from a side of said stab body through a stab body side port;   a stab receptacle mounted on the wellhead and having a stab receiving bore therethrough for receiving said stab body therewithin;   said stab receptacle having a receptacle flow bore therethrough, one end of said receptacle flow bore being in fluid communication with said stab receiving bore and the other end of said receptacle flow bore exiting said stab receptacle and being in fluid communication with the flowline;   means for establishing fluid communication between said stab body side port and said one end of said receptacle flow bore when said stab body is received within said stab receiving bore, including means disposed on said stab member for orienting said stab member with respect to said Christmas tree for ensuring the alignment of said stab body side port with said one end of said receptacle flow bore when said stab body is received within said stab receiving bore; and   first and second sealing means disposed on said stab body above and below said stab body side port, respectively, for sealing engagement with the walls of said stab receiving bore above and below said one end of said receptacle flow bore for establishing a non-blow-apart, fluid pressure sealed flow passage between said stab body bore of said stab member and said receptacle flow bore of said stab receptacle when said stab body is landed within said stab receiving bore.   
     
     
       2. Apparatus according to claim 1, wherein said stab body includes a stab flange at its upper end having a plurality of bolt holes disposed about its circumference for receiving bolts therewithin for mounting said stab flange, and said orienting means includes a relatively enlarged bolt hole among said plurality of holes for receiving a correspondingly relatively enlarged bolt therewithin. 
     
     
       3. Apparatus for sealingly connecting a flow bore of a wellhead to a flowline, comprising: a stab member including a stab body, said stab body having a stab body bore therethrough, one end of said stab body bore exiting from said stab body and being in fluid communication with the flow bore and the other end of said stab body bore exiting from a side of said stab body through a stab body side port;   a stab receptacle mounted on the wellhead and having a stab receiving bore therethrough for receiving said stab body therewithin;   said stab receptacle having a receptacle flow bore therethrough, one end of said receptacle flow bore being in fluid communication with said stab receiving bore and the other end of said receptacle flow bore exiting said stab receptacle and being in fluid communication with the flowline;   means for establishing fluid communication between said stab body side port and said one end of said receptacle flow bore when said stab body is received within said stab receiving bore; and   first and second sealing means disposed on said stab body above and below said stab body side port, respectively, for sealing engagement with the walls of said stab receiving bore above and below said one end of said receptacle flow bore for establishing a non-blow-apart, fluid pressure sealed flow passage between said stab body bore of said stab member and said receptacle flow bore of said stab receptacle when said stab body is landed within said stab receiving bore, said first and second sealing means being sized such that fluid pressure acting from within said flow passage on cross-sectional areas of said first and second sealing means exposed to such fluid pressure effects a reverse blow-apart force tending to prevent withdrawal of said stab member from said stab receiving bore.   
     
     
       4. Apparatus according to claim 3, wherein the cross-sectional area of said second sealing means exposed to such fluid pressure acting from within said flow passage is larger than the cross-sectional area of said first sealing means exposed to such fluid pressure. 
     
     
       5. Apparatus for sealingly connecting a flow bore of a wellhead to a flowline, comprising: a stab member including a stab body, said stab body having a stab body bore therethrough, one end of said stab body bore exiting from said stab body and being in fluid communication with the flow bore and the other end of said stab body bore exiting from a side of said stab body through a stab body side port;   a stab receptacle mounted on the wellhead and having a stab receiving bore therethrough for receiving said stab body therewithin;   said stab receptacle having a receptacle flow bore therethrough, one end of said receptacle flow bore being in fluid communication with said stab receiving bore and the other end of said receptacle flow bore exiting said stab receptacle and being in fluid communication with the flowline;   means for establishing fluid communication between said stab body side port and said one end of said receptacle flow bore when said stab body is received within said stab receiving bore;   first and second sealing means disposed on said stab body above and below said stab body side port, respectively, for sealing engagement with the walls of said stab receiving bore above and below said one end of said receptacle flow bore for establishing a non-blow-apart, fluid pressure sealed flow passage between said stab body bore of said stab member and said receptacle flow bore of said stab receptacle when said stab body is landed within said stab receiving bore; and   means in said stab body bore and said receptacle flow bore for reducing the turbulence of fluid flow through said bores, said turbulence-reducing means including an enlarged-diameter portion of said stab body bore terminating at and extending from said side port, a substantially non-enlarged-diameter portion of said receptacle flow bore terminating at and extending from said one end of said receptacle flow bore and joining an enlarged-diameter portion of said receptacle flow bore that terminates at and joins a substantially non-enlarged diameter portion of said receptacle flow bore, wherein diameter is measured transverse to an axis of flow within said bores.   
     
     
       6. Apparatus according to claim 5, wherein said turbulence-reducing means includes a tapered portion of said stab body bore extending from the end of said enlarged portion opposite from said side port, said tapered portion narrowing in internal diameter to terminate in a substantially non-enlarged-diameter portion of said stab body bore. 
     
     
       7. Apparatus according to claim 6, wherein said enlarged-diameter portion of said receptacle flow bore is a stepped portion having a long tapered portion intersecting said one end of said receptacle flow bore and increasing in internal diameter as it extends therefrom, an expanded-diameter portion communicating with the end of said long tapered portion opposite from said one end of said receptacle flow bore and extending away from said long tapered portion, and a short tapered portion extending from the end of said expanded-diameter portion opposite from said long tapered portion and narrowing in internal diameter as it extends away from said expanded-diameter portion. 
     
     
       8. Apparatus for sealingly connecting a flow bore of a wellhead to a flowline, comprising: a stab member including a stab body, said stab body having a stab body bore therethrough, one end of said stab body bore exiting from said stab body and being in fluid communication with the flow bore and the other end of said stab body bore exiting from a side of said stab body through a stab body side port;   a stab receptacle mounted on the wellhead and having a stab receiving bore therethrough for receiving said stab body therewithin;   said stab receptacle having a receptacle flow bore therethrough, one end of said receptacle flow bore being in fluid communication with said stab receiving bore and the other end of said receptacle flow bore exiting said stab receptacle and being in fluid communication with the flowline;   means for establishing fluid communication between said stab body side port and said one end of said receptacle flow bore when said stab body is received within said stab receiving bore;   first and second sealing means disposed on said stab body above and below said stab body side port, respectively, for sealing engagement with the walls of said stab receiving bore above and below said one end of said receptacle flow bore for establishing a non-blow-apart, fluid pressure sealed flow passage between said stab body bore of said stab member and said receptacle flow bore of said stab receptacle when said stab body is landed within said stab receiving bore; and   upper and lower retainer ring means disposed around said stab body above and below said second sealing means, respectively, for facilitating stab-in of said stab body into said stab receiving bore in the event said stab body is misaligned with said stab receiving bore.   
     
     
       9. Apparatus according to claim 8, wherein said upper and lower retainer ring means include a retainer ring having an external chamfer surface. 
     
     
       10. The apparatus according to claim 9, wherein said retainer ring is a split ring adapted to protect one of said sealing means. 
     
     
       11. Apparatus according to claim 9, wherein said retainer ring is disposed in a ring groove around said stab body, said ring groove having upper and lower ring groove ledges and an axially extending groove face therebetween, and the inside diameter of said retainer ring is greater than the outside diameter of said groove face. 
     
     
       12. Apparatus according to claim 11, wherein said second sealing means includes upper and lower elastomeric seal ring elements, and said stab body includes a circumferential seal ridge portion separating said seal ring elements, said seal ridge portion having an outside diameter greater than the outside diameter of said stab body adjacent said seal ridge portion. 
     
     
       13. Apparatus according to claim 12, wherein each of said upper and lower retainer ring means includes one of said retainer rings, said retainer ring of said lower retainer ring means having an upwardly facing ring seal surface on which the bottom face of said lower seal ring element is disposed, and said retainer ring of said upper retainer ring means having a downwardly facing ring seal surface in engagement with a top face of said upper seal ring element, and said seal ridge portion having an upwardly facing ridge seal surface on which a bottom face of said upper seal ring element is disposed and a downwardly facing ridge seal surface in engagement with a top face of said lower seal ring element. 
     
     
       14. Apparatus according to claim 13, wherein said chamfer surface of said retainer ring of said lower retainer ring means includes a downwardly and outwardly facing, downwardly narrowing tapered surface and said chamfer surface of said retainer ring of said upper retainer ring means includes an upwardly and outwardly facing, upwardly narrowing tapered surface. 
     
     
       15. Apparatus according to claim 14, wherein said seal ring elements are lip seals. 
     
     
       16. Apparatus for sealingly connecting a flow bore of a wellhead to a flowline, comprising: a stab member including a stab body, said stab body having a stab body bore therethrough, one end of said stab body bore exiting from said stab body and being in fluid communication with the flow bore and the other end of said stab body bore exiting from a side of said stab body through a stab body side port;   a stab receptacle mounted on the wellhead and having a stab receiving bore therethrough for receiving said stab body therewithin;   said stab receptacle having a receptacle flow bore therethrough, one end of said receptacle flow bore being in fluid communication with said stab receiving bore and the other end of said receptacle flow bore exiting said stab receptacle and being in fluid communication with the flowline;   means for establishing fluid communication between said stab body side port and said one end of said receptacle flow bore when said stab body is received within said stab receiving bore;   first and second sealing means disposed on said stab body above and below said stab body side port, respectively, for sealing engagement with the walls of said stab receiving bore above and below said one end of said receptacle flow bore for establishing a non-blow-apart, fluid pressure sealed flow passage between said stab body bore of said stab member and said receptacle flow bore of said stab receptacle when said stab body is landed within said stab receiving bore; and   stab receptacle mounting means for mounting said stab receptacle on the wellhead for rigidly resisting forces acting on said stab receptacle in a vertical direction and for permitting lateral and rotational deflection of said stab receptacle with respect to the wellhead when forces act on said stab receptacle from other than a vertical direction.   
     
     
       17. Apparatus according to claim 16, wherein said mounting means including a plurality of mounting brackets attached to said stab receptacle near its upper end, and including a mounting stud for each said bracket attached at its upper end to said bracket and at its lower end to the wellhead, said studs being relatively long in relation to their transverse thickness. 
     
     
       18. Apparatus according to claim 17, including mounting plate means mounted on said stab receptacle and cooperable with retainer plate means mounted on the wellhead for limiting the lateral and rotational deflection of said stab receptacle with respect to the wellhead. 
     
     
       19. A pressure-balanced stab assembly for connecting flow-conducting conduits, comprising: a stab member having a first flow bore therethrough;   a receptacle member having a receiving bore therethrough for receiving said stab member therewithin, and a second flow bore intersecting said receiving bore and communicating with the exterior of said receptacle member;   said first flow bore communicating with said second flow bore at a communication region within said receiving bore when said stab member is landed within said receiving bore;   upper and lower sealing means disposed on said stab member for sealing engagement with the walls of said receiving bore above and below said communication region when said stab member is landed within said receiving bore, said upper and lower sealing means having substantially equal cross-sectional areas exposed to pressure from fluids within said communication region; and   means disposed on said stab member above and below said lower sealing means for protecting said sealing means during stab-in of said stab member into said receiving bore and for facilitating such stab-in in the event said stab member is misaligned with said receiving bore.   
     
     
       20. A stab assembly according to claim 19, and including means in said first and second flow bores for reducing the turbulence of fluid flow through said bores. 
     
     
       21. A stab assembly according to claim 19, wherein said lower sealing means protecting means and stab-in facilitating means includes upper and lower split retainer rings disposed around said stab member above and below said lower sealing means, respectively, said split retainer rings each having an external chamfer surface. 
     
     
       22. A stab assembly according to claim 21, wherein each retainer ring is disposed in a groove around the periphery of said stab member, and there is a gap between the inner diameter surface of said retainer rings and the opposing groove face of said grooves. 
     
     
       23. A stab assembly according to claim 22, wherein said lower retainer ring chamfer surface is a downwardly and outwardly facing, downwardly narrowing frustoconical surface and said upper retainer ring chamfer surface is an upwardly and outwardly facing, upwardly narrowing frustoconical surface. 
     
     
       24. A stab assembly according to claim 23, wherein said lower sealing means includes a plurality of elastomeric seal ring elements separated by a raised, circumferentially extending ridge surface portion of said stab member. 
     
     
       25. A stab assembly according to claim 24, wherein said upper sealing means includes a plurality of elastomeric seal ring elements, and said seal ring elements are lip seals having their lips facing toward said communication region.